This invention relates to surgical instruments which have at least two triggers to actuate the business end of the instrument to manipulate bodily tissue. More specifically, it relates to surgical instruments which have a frame, and clamping and firing triggers mounted to the frame for causing the clamping of bodily tissue and the firing of staples into the clamped tissue at the business end of the instrument.
Surgical instruments typically include a frame for manipulating the instrument and an "end effector" remote from the frame at the business end of the instrument to cause the manipulation of bodily tissue in some desired fashion. Frequently, the actuation of the end effector to cause the manipulation of the tissue is carried out when the surgeon squeezes or depresses a trigger or lever mounted to the frame. In many surgical instruments, more than one trigger or lever mounted to the frame is necessary to effect the actuation of different functions which the end effector is designed to perform during the manipulation of the tissue. A classic example of where two triggers or levers mounted to the frame have been used is with surgical staplers.
One particular type of surgical stapler, frequently referred to as a "linear stapler", fires vertical rows of staples into bodily tissue. It has an end effector which includes a cartridge carrying a plurality of staples and an anvil upon which the staples are formed. The cartridge and anvil are movable relative to each other from an open position where tissue is placed between the cartridge and anvil to a closed position where the cartridge and anvil are adjacent to each other and the tissue positioned between them is clamped. A linear stapler can be particularly designed for applications involving minimally invasive surgery, where surgery is performed through small openings, or conventional "open" surgery.
Linear staplers have clamping and firing triggers or levers mounted to the frame of the stapler. When the surgeon squeezes or depresses the clamping trigger or lever, the bodily tissue positioned between the cartridge and anvil is clamped as the components of the end effector move to their closed position. Subsequently, the surgeon squeezes or depresses the firing trigger or lever to fire the staples from the cartridge against the anvil to staple the clamped tissue. Obviously, the way in which the clamping and firing triggers are mounted to the frame of the linear stapler has a significant impact on the operability and "feel" of the instrument from the surgeon's perspective. Additionally, the mounting affects the cost and reproducibility of the stapler for manufacturing on a commercial scale.
Excellent examples of preferred clamping and trigger mounting techniques for linear staplers are described in U.S. Pat. Nos. 5,307,976 and 5,452,836. These parents describe a linear stapler which has a frame and a hand grip handle descending from the frame for the surgeon to grip. The clamping and firing triggers likewise descend from the frame and are pivotally mounted to it for actuation. The clamping trigger is initially positioned so that the surgeon can grip the hand grip with the palm of his hand and extend his fingers to grasp the clamping trigger and squeeze it. Upon squeezing, the clamping trigger pivots counterclockwise towards the hand grip handle. In so doing, the firing trigger similarly pivots from its original position approximately 45.degree. from the underside of the frame to an intermediate position located at about the position which represented the original position of the clamping trigger. Accordingly, once the surgeon has fully squeezed the clamping trigger and it is positioned adjacent to the hand grip handle, the surgeon is then in position to grasp and squeeze the firing trigger. This is an outstanding mechanism, but, of course, there is always room for improvement. Specifically, the pivotal movement of the clamping and firing triggers is dependent on each other. In other words, movement of the clamping trigger necessarily entails a corresponding movement of the firing trigger. Consequently, the clamping and firing triggers may require the use of precision parts to ensure precise movement of the triggers in tandem during operation, resulting in an increase in manufacturing costs and design complexity.
Another feature of a linear stapler which would be desirable is a feature which enables the surgeon to squeeze the clamping trigger into an intermediate or partially closed position. This feature would allow the surgeon to conveniently and properly position the stapler before full closure and stapling is accomplished. Once the positioning of the stapler is set, it would be desirable if the surgeon could then squeeze the clamping trigger from its partially closed position to its fully closed position for tissue clamping. Additionally, it would also be desirable if the clamping trigger of the stapler could be returned to its original fully opened position by overriding the partially closed position following the stapling of tissue.
Accordingly, it would be beneficial to develop a surgical instrument, particularly a linear stapler, which incorporates clamping and firing triggers which are pivotal toward a hand grip handle, but which are independent of each other for the pivotal movement. Furthermore, it would be beneficial to develop a stapler which has a clamping trigger capable of actuation to an intermediate or partially closed position. Ideally, it would be possible to override the partially closed position of the clamping trigger following the stapling of the tissue when opening the instrument.